Metal plate shaping method

ABSTRACT

There are provided a step of preparing a plurality of metal plates that has a concave shape in a center principal portion except a predetermined peripheral portion, and a step of executing a thermal treatment to the plurality of metal plates in such a state that a plurality of metal plates are stacked to mate the predetermined peripheral portion with each other and also predetermined peripheral portions are pushed.

BACKGROUND OF THE INVENTION

[0001] 1) Field of the Invention

[0002] The present invention relates to a metal plate shaping methodand, more particularly, a method of shaping a metal plate (sealingplate) employed in an organic EL display device having an organic EL(Electroluminescence) layer, etc.

[0003] 2) Description of the Related Art

[0004] In recent years, the organic EL element takes the attention asthe self-light emitting element. The organic EL element has suchfeatures that this element has the good display characteristic becauseof its self-light emitting characteristic, this element is excellent inshock resistance because such element is the perfect solid stateelement, power consumption of this element is low, etc. Therefore, theutilization as the light-emitting element in various display devices isexpected.

[0005]FIG. 13 is a sectional view showing an example of the organic ELdisplay device. In this organic EL display device, as shown in FIG. 13,an organic EL element array 102 is formed on a transparent glasssubstrate 100. The organic EL element has a structure in which anorganic EL layer is put between a cathode and an anode. In the organicEL display device, holes injected from the anode and electrons injectedfrom the cathode are recombined with each other in the inside of theorganic EL layer to emit the light, and then this light passes throughthe transparent anode and is emitted to the outside. Thus, the displayimage can be obtained.

[0006] In such organic EL element, the dot-like or circle-likenon-emission display defect that is called the dark spot (dark defectspot) is ready to occur since separation of the electrode and theorganic EL layer proceeds due to penetration of the moisture, etc.

[0007] Therefore, a passivation film is formed on the organic EL elementarray 102 and also the organic EL element array 102 is capped by a backcap 108 that has a concave portion 108 a in its center principalportion. A peripheral portion of the back cap 108 except the concaveportion 108 a is bonded to a peripheral portion of the glass substrate100 by an adhesive layer 101.

[0008] In this manner, the organic EL element array 102 is arranged inthe concave portion 108 a of the back cap 108, and an inert gas thatdoes not contain the moisture, or the like is filled in a space 104 ofthe concave portion 108 a. And an adsorbent material 106 adsorbingmoisture is arranged in a bottom portion of a concave portion of theback cap 108.

[0009] According to such configuration, not only the penetration of themoisture into the organic EL element array 102 from the outside can beprevented, but also the organic EL element array 102 can be protectedfrom the mechanical impact.

[0010] In many cases, the glass substrate is employed as the back cap108. The glass substrate has good flatness of the surface, and can mateits coefficient of thermal expansion with the glass substrate 100 on theside of the organic EL element. Therefore, such glass substrate isconvenient from such a viewpoint that the reliability of the bonding canbe improved.

[0011] In the prior art, the back cap 108 is manufactured by forming theconcave portion in the predetermined center portion of the glasssubstrate by virtue of the sand blast or the wet etching.

[0012] Meanwhile, since not only a thickness of an adsorbent material106 but also the space 104 between the adsorbent material 106 and theorganic EL element array 102 must be assured, a depth of the concaveportion 108 a of the back cap 108 must be formed relatively deep (e.g.,about 0.5 mm).

[0013] For this reason, when the concave portion is formed in the glasssubstrate by the sand blast or the wet etching, a work efficiency is lowbecause a large amount of working is required, and thus an increase incost is brought about. Also, because a predetermined strength isrequired of the glass substrate after the concave portion is formed, therelatively thick glass substrate must be used. As a result, a thicknessof the organic EL display device is also increased.

[0014] As the countermeasure, the trial to employ the metal plate as theback cap 108 in place of the glass substrate was made. This trial issuch a method that the concave portion is formed in the predeterminedcenter portion of the metal plate by shaping the metal plate by virtueof the stamping, or the like.

[0015] However, according to this method, the problem such that theincrease in cost and increase in the thickness can be overcome,nevertheless the metal plate is inferior in flatness of the surface tothe glass substrate and also the flatness of the surface is furtherdeteriorated by the stress caused in the stamping. Therefore, such aproblem is caused that the reliability of the bonding between the metalplate and the glass substrate on the organic EL element side is lowered.As a result, it is possible that, since the moisture penetrates into theorganic EL element from the outside, the above-mentioned display defectis caused.

SUMMARY OF THE INVENTION

[0016] It is an object of the present invention to provide a metal plateshaping method capable of improving the reliability of joint between ametal plate and a substrate of a display device by improving a flatnessof an adhesive surface of the metal plate.

[0017] The present invention provides a metal plate shaping method thatcomprises the steps of preparing a metal plate that has a concave shapein a center principal portion except a predetermined peripheral portion;and executing a thermal treatment in such a state that a plurality ofmetal plates are stacked to mate the predetermined peripheral portionwith each other and also predetermined peripheral portions are beingpushed.

[0018] In the present invention, first the metal plate that has theconcave shape in the center principal portion except the predeterminedperipheral portion is prepared. In this step, the concave shape may beformed by pushing the center principal portion except the predeterminedperipheral portion by virtue of the stamping, or the concave shape maybe formed by etching the center principal portion of the metal plate toreduce its thickness. Otherwise, the concave shape may be formed byetching the center principal portion of the metal plate to reduce thethickness and then pushing the center principal portion by virtue of thestamping.

[0019] Then, the thermal treatment is applied to the metal plate in sucha state that a plurality of metal plates are stacked to bring thepredetermined peripheral portion into contact with each other, forexample, and also a predetermined pushing pressure is applied to thepredetermined peripheral portions by clamping the peripheral portions byvirtue of the clamping jig, or the like. At this time, when the concaveshape is formed in the metal plate by the stamping, a plurality of metalplates may be stacked while inserting the spacer between thepredetermined peripheral portions to prevent the situation that portionsof the metal plates except the predetermined peripheral portions arebrought into contact mutually and thus deformed.

[0020] In this manner, because the thermal treatment is applied to themetal plates in the state that the predetermined peripheral portions arepushed, not only the step caused due to the stress (internal stress) inthe metal plate itself but also the step caused due to the stress by thestamping can be corrected. As a result, the flatness that is equal to orhigher than the glass substrate can be obtained on the surface of thepredetermined peripheral portion of the metal plate.

[0021] Then, the surface of the predetermined peripheral portion of themetal plate is bonded to the peripheral portion of the substrate of thedisplay device as the bonding surface, and the concave portion in thecenter principal portion of the metal plate acts as the back cap(sealing plate) that covers the element forming region within apredetermined space.

[0022] As described above, because the bonding surface of thepredetermined peripheral portion of the metal plate has the flatnessthat is equal to or higher than the glass substrate, the reliability ofthe jointing of the substrate of the display device and the metal platecan be improved. Therefore, if the metal plate shaped by the method ofthe present invention is employed as the back cap of the organic ELdisplay element, penetration of the moisture into the organic EL elementfrom the outside can be prevented and thus the generation of the displaydefect can be prevented.

[0023] Also, the metal plate can be employed as the back cap. Therefore,unlike the case of the glass substrate, the increase in cost can besuppressed by using the stamping, and also the sufficient mechanicalstrength can be obtained even if the thickness of the back cap isthinned. As a result, the thin organic EL display device can be easilymanufactured.

[0024] In the above metal plate shaping method, it is preferable thatthe metal plate is formed of any one selected from a group consisting ofan alloy of nickel (Ni) and iron (Fe), an alloy of nickel (Ni), iron(Fe) and cobalt (Co), tungsten (W), and molybdenum (Mo).

[0025] The coefficient of thermal expansion of the Ni—Fe alloy, theNi—Fe—Co alloy, W or Mo is close to the glass substrate of the displaydevice. Therefore, if the metal plate made of one of these materials isemployed as the back cap of the organic EL display element,disadvantages such that, when the stress is applied by the heat, or thelike, cracks are generated in the bonding layer due to difference in thecoefficient of thermal expansion, and others can be overcome. As aresult, the reliability of the jointing of the substrate of the displaydevice and the back cap can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIGS. 1A to 1D are sectional views showing a metal plate shapingmethod according to a first embodiment of the present invention, whereinFIG. 1B is a sectional view taken along a I-I line in FIG. 1D (planview);

[0027]FIG. 2A is a perspective view showing an example of the clampingjig employed in the metal plate shaping method according to embodimentsof the present invention, and FIG. 2B is a sectional view taken along aII-II line in FIG. 2A;

[0028]FIG. 3A is a sectional view showing an example of the thermaltreatment equipment employed in the metal plate shaping method accordingto the embodiments of the present invention, and FIG. 3B is a viewshowing an example of the temperature profile in a furnace of thethermal treatment equipment in FIG. 3A;

[0029]FIG. 4 is a sectional view showing a metal plate (back cap)manufactured by the metal plate shaping method according to a firstembodiment of the present invention;

[0030]FIG. 5 is a sectional view showing an example of an organic ELdisplay device in which the metal plate in the first embodiment of thepresent invention is applied as the back cap;

[0031]FIG. 6 is a plan view showing an experimental sample;

[0032]FIGS. 7A to 7C are views showing a flatness of a surface of themetal plate before a planarizing process is applied;

[0033]FIGS. 8A to 8C are views showing the flatness of the surface ofthe metal plate that is subjected to the planarizing process accordingto the metal plate shaping method of the present embodiment;

[0034]FIGS. 9A to 9C are views showing the flatness of the surface ofthe metal plate that is subjected to the planarizing process accordingto the metal plate shaping method of the present embodiment after themetal plate is bent;

[0035]FIG. 10 is a sectional view showing a metal plate shaping methodaccording to a second embodiment of the present invention;

[0036]FIGS. 11A to 11E are sectional views showing a metal plate shapingmethod according to a third embodiment of the present invention;

[0037]FIGS. 12A to 12D are sectional views showing a metal plate shapingmethod according to a fourth embodiment of the present invention; and

[0038]FIG. 13 is a sectional view showing an example of an organic ELdisplay device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] Embodiments of the present invention will be explained withreference to the accompanying drawings hereinafter.

[0040] (First Embodiment)

[0041]FIGS. 1A to 1D are views showing a metal plate shaping methodaccording to a first embodiment of the present invention, FIGS. 2A and2B are views showing an example of the clamping jig employed in themetal plate shaping method according to present embodiments, FIG. 3A isa sectional view showing an example of the thermal treatment equipmentemployed in the metal plate shaping method according to the presentembodiments, FIG. 3B is a view showing an example of the temperatureprofile in the furnace of the thermal treatment equipment in FIG. 3A,FIG. 4 is a sectional view showing a metal plate (back cap) manufacturedby the metal plate shaping method according to the present embodiment,and FIG. 5 is a sectional view showing an example of an organic ELdisplay device in which the metal plate in the present embodiment isapplied as the back cap.

[0042] In the metal plate shaping method according to the firstembodiment of the present invention, as shown in FIG. 1A, first a metalplate 10 a that is made of Ni—Fe alloy (42 alloy), or the like and has athickness of about 0.25 to 0.3 mm, for example, and a die 26 areprepared. In this case, as the metal plate 10 a, Ni—Fe—Co alloy (Kovar),tungsten (W), molybdenum (Mo), aluminum (Al), stainless (SUS304), or thelike may be employed in addition to the Ni—Fe alloy.

[0043] Basically this die 26 is composed of a punch 20, a clampingmember 22, and a supporting member 24. The metal plate 10 a is insertedbetween the clamping member 22 and the supporting member 24, and then apredetermined portion of the metal plate 10 a is pushed by the punch 20to roll. Thus, the concave portion is formed.

[0044] Then, the metal plate 10 a is inserted into such die 26, and themetal plate 10 a is pushed by the punch 20 to roll. Thus, as shown inFIGS. 1B and 1D, a metal plate 10 consisting of a bonded portion 10 zprovided in a predetermined peripheral portion, a rolled portion 10 yrolled to be connected to the bonded portion 10 z, and a pushed portion10 x connected to the rolled portion 10 y is obtained. A concave portion11 consisting of the pushed portion 10 x and the rolled portion 10 y isformed in a center principal portion of the metal plate 10. Because thisrolled portion 10 y is formed by rolling a neighboring portion of thepushed portion 10 x of the metal plate when the pushed portion 10 x ofthe metal plate 10 is pushed, a thickness of the rolled portion 10 y isreduced rather than the bonded portion 10 z and the pushed portion 10 x.

[0045] This metal plate 10 serves as a back cap (sealing plate) of adisplay device such as an organic EL display device, etc. The bondedportion 10 z is bonded to a peripheral portion of the glass substrate ofthe display device via the adhesive layer, and an organic EL elementarray is arranged in a space of the concave portion 11 and is capped bythe metal plate 10.

[0046] In this manner, it is preferable from the viewpoint of improvingthe reliability of the bonding against the stress such as heat, etc.that, since the metal plate 10 is bonded to the glass plate via theadhesive layer, the Ni—Fe alloy (e.g., 4.5 ppm), a coefficient ofthermal expansion of which is close to the glass substrate (e.g., 4.8ppm), of the above metal materials should be employed. Also, it is alsopreferable from the similar viewpoint that Ni—Fe—Co alloy, W or Moshould be employed in addition to the Ni—Fe alloy.

[0047] As described above, the metal plate is inferior in flatness ofits surface to the glass substrate (glass substrate: 10 to 30 μm, forexample, metal plate: 50 μm or more, for example), and then the flatnessis further deteriorated by the stress applied by the stamping. Hence,the reliability of bonding is lowered by the heat or the mechanicalimpact after this metal plate 10 is bonded to the display substrate, andit is possible that the display defect occurs in the organic EL displaydevice because the moisture penetrates into the display device from thebonded portion.

[0048] The metal plate shaping method according to the first embodimentof the present invention is invented to planarize a bonding surface 10 sof the metal plate 10, which is shaped in this manner, to the extentthat is equal to or higher than the flatness of the glass substrate.

[0049] Next, a method of planarizing the bonding surface 10 s of themetal plate 10 will be explained hereunder.

[0050] First, as shown in FIG. 1C, a lower plate 12 made of cementedcarbide hard metal or ceramic is prepared. A plurality of metal plates10 are arranged to be stacked on the lower plate 12 such that thebonding surface 10 s of the metal plate 10, which is shaped into theshape shown in FIG. 1B, is directed to the lower plate 12 side.

[0051] At this time, the bonding surface 10 s of the lowermost metalplate 10 contacts to the lower plate 12, and also a plurality of metalplates 10 are stacked such that their bonded portions 10 z come intocontact with each other. Also, since a thickness of the rolled portion10 y of the metal plate 10 is thinned rather than other portions by therolling, a plurality of metal plates 10 are stacked in the situationthat their rolled portions 10 y do not contact mutually to form aclearance 13 therebetween.

[0052] In this case, in the first embodiment, the pushed portions 10 xcome into contact mutually when a plurality of metal plates 10 arestacked. Thus, if the number of sheets of the metal plate 10 isincreased, it is supposed that the lower metal plates 10 are deformedparticularly by their weights. Therefore, it is preferable that thenumber of stacked sheets should be set to about 10 to 20.

[0053] Next, explanation of a clamping jig that clamps a plurality ofmetal plates 10, which are stacked on the lower plate 12, will be madehereunder. As shown in FIG. 2A and FIG. 2B, in a clamping jig 40, aclamping plate 30 having a convex portion 30 a in the area, whichcorresponds to the bonded portion 10 z of the metal plate 10, and aconcave portion 30 b in the areas, which correspond to the pushedportion 10 x and the rolled portion 10 y of the metal plate 10, isarranged on the lower plate 12 on which a plurality of metal plates 10are stacked and arranged, as described above. As a result, the bondedportions 10 z formed on the peripheral portions of the metal plates 10are put between the peripheral portion of the lower plate 12 and theconvex portion 30 a of the clamping plate 30.

[0054] An upper plate 32 in which a convex portion 32 a is provided inthe area that corresponds to the peripheral portion of the clampingplate 30 is arranged on this clamping plate 30. Also, side surfaceguides 34 which support the upper plate 32 and the lower plate 12 areprovided at a beginning portion and an end portion of the upper plate 32and the lower plate 12 respectively.

[0055] Then, an opening portion 32 b is formed at the center portion ofthe upper plate 32. A cap screw 36 is inserted into the opening portion32 b. A predetermined pushing force is applied to the clamping plate 30under the upper plate 32 by screwing the cap screw 36. Like the lowerplate 12, the clamping plate 30 and the upper plate 32 are made ofcemented carbide hard metal, ceramic, or the like.

[0056] The clamping jig 40 is constructed as above. If the cap screw 36is screwed into a predetermined position, the bonded portions 10 z ofthe metal plates 10 are clamped by the convex portion 30 a of theclamping plate 30 and the peripheral portion of the lower plate 12 tohave a predetermined pressure. In addition, as explained in FIG. 1C,since the rolled portions 10 y of plural metal plates 10 is reduced inthickness rather than other portions, such rolled portions 10 y nevercontact mutually. Therefore, such a drawback is not generated that therolled portions 10 y are affected by the pushing of the bonded portions10 z and thus pushed/deformed unnecessarily. At this time, the bondedportions 10 z of the metal plates 10 are pushed by the load of 1 g/mm²,for example.

[0057] In this case, in the above example, the mode in which a pluralityof metal plates 10 are stacked and then clamped by the clamping jig 40is exemplified. But a one sheet of metal plate 10 may be clamped by theclamping jig 40.

[0058] Then, the metal plates 10 the bonded portions 10 z of which areclamped by the clamping jig 40 are thermally treated in the thermaltreatment equipment. As shown in FIG. 3A, a thermal treatment equipment50 employed in the present embodiment is a belt conveyer furnace thatcomprises basically a mesh-like metal belt conveyer 42 for carrying thethermally treated object at a predetermined speed, a thermal treatmentfurnace 44, and heaters 48 arranged on the top side and the bottom sideof the thermal treatment furnace 44 respectively. A cooling chamber 44 ais provided adjacent to the thermal treatment furnace 44 in the carryingdirection side, and a cooling fan 46 is fitted to the top portion ofthis cooling chamber 44 a.

[0059] Nonoxidizing gas supplying pipes 45 and a nonoxidizing gasexhausting pipe 47 are provided at the top portion of the thermaltreatment furnace 44. A nonoxidizing gas such as a nitrogen gas, anargon gas, or the like is supplied to the inside of the thermaltreatment furnace 44 via the nonoxidizing gas supplying pipes 45, andthen is exhausted to the outside of the thermal treatment furnace 44 viathe nonoxidizing gas exhausting pipe 47.

[0060] The thermally treated object is carried into the thermaltreatment furnace 44 via a loading portion 44 x by the belt conveyer 42at a predetermined carrying speed, then is subjected to thepredetermined thermal treatment during the passage in the thermaltreatment furnace 44, then is cooled in the cooling chamber 44 a, andthen is carried out to the outside via an unloading portion 44 y.

[0061] The metal plates 10 that are in the state being clamped by theabove clamping jig 40 are thermally treated by using such thermaltreatment equipment 50. A temperature profile in the thermal treatmentfurnace 44 is given such that, as shown in FIG. 3B, first thetemperature is increased up to 600 to 800° C., preferably 700° C. at apredetermined programming rate, then this temperature is held for 1 to 2hour, for example, to execute the thermal treatment, and then thetemperature is decreased into about 150° C., for example, in the coolingchamber 44 a.

[0062] The temperature profile is set by adjusting a set temperature ofthe heater 48, a carrying speed (e.g., 20 to 200 mm/min) of the beltconveyer 42, a flow rate of the nitrogen gas, etc. In this case, fromthe viewpoint such that discoloration must be suppressed by preventingthe oxidation of the metal plate 10, preferably the nonoxidizing gassuch as nitrogen, argon, or the like should be employed as theatmosphere in the thermal treatment furnace 44. But such atmosphere maybe set to the atmospheric atmosphere.

[0063] Then, after the clamping jig 40 is carried from the coolingchamber 44 a to the outside by the belt conveyer 42 and then thetemperature comes down to a room temperature, such clamping jig 40 isdisassembled and then a plurality of metal plates 10 are detachedindividually. With the above, as shown in FIG. 4, the metal plate 10that is worked by the metal plate shaping method according to the firstembodiment of the present invention can be manufactured. Since thebonded portion 10 z of the metal plate 10 is subjected to the thermaltreatment at the temperature of about 700° C., for example, in thesituation that such portion is clamped by a predetermined force that isapplied by the clamping jig 40, the bonded portion 10 z of the metalplate 10 containing the bonding surface 10 s is made flat and a degreeof flatness can be set to about 50 μm or less.

[0064] As described above, because the planarizing process according tothe present embodiment is applied, not only the step caused due to thestress (internal stress) contained in the metal plate 10 itself but alsothe step caused due to the stress in the stamping can be corrected. As aresult, the flatness that is equal to or higher than the glass substratecan be obtained.

[0065] Then, as shown in FIG. 5, the metal plate 10 in the presentembodiment acts as the back cap (sealing plate) when the bonding surface10 s is bonded to the peripheral portion of the transparent glasssubstrate 60, on which the predetermined organic EL element array 64 isformed, via the adhesive layer 62. Also, an adsorbent material 66 isadhered onto a bottom surface of the concave portion 11 of the metalplate 10.

[0066] In the metal plate 10 in the present embodiment, because theflatness that is equal to or higher than the glass substrate can beobtained, the metal plate 10 can be bonded to the glass substrate 60with the good adhesion and the high reliability. As a result, since thepenetration of the moisture into the organic EL element array 64 fromthe outside can be prevented, generation of the display defect in theorganic EL display device can be prevented.

[0067] Also, the metal plate can be employed as the back cap. Therefore,unlike the case that the glass substrate is employed, not only theincrease in cost can be suppressed by using the stamping but also thesufficient mechanical strength can be obtained even if a thickness ofthe back cap is reduced. As a result, the thin organic EL display devicecan be easily manufactured.

[0068] In addition, since the Ni—Fe alloy, or the like, a coefficient ofthermal expansion of which is close to the glass substrate 60 of thedisplay device, is employed as the material of the metal plate 10, thereliability of the bonding against the stress such as thermal stress,etc. can be further improved, like the case that the glass substrate isemployed.

[0069] The inventors of this application have made experiments tovalidate effects of the metal plate shaping method of the presentembodiment. FIG. 6 is a plan view showing an experimental sample, FIGS.7A to 7C are views showing the flatness of the surface of the metalplate before the planarizing process is applied, FIGS. 8A to 8C areviews showing the flatness of the surface of the metal plate that issubjected to the planarizing process according to the metal plateshaping method of the present embodiment, and FIGS. 9A to 9C are viewsshowing the flatness of the surface of the metal plate that is subjectedto the planarizing process according to the metal plate shaping methodof the present embodiment after the metal plate is bent.

[0070] First, as shown in FIG. 6, a ring-like metal plate 10 b, whichcorresponds to the above bonded portion 10 z of the metal plate 10, isformed as an experimental sample by etching the metal plate made of theNi—Fe alloy. Then, the flatness (a degree of flatness) in theinfinitesimal area (X axis×Y axis) of the surface of the ring-like metalplate 10 b was measured by the non-contact type step measuringapparatus.

[0071] As shown in FIGS. 7A to 7C, it was checked that a step of about±10 μm is generated in three infinitesimal areas of the surface of thering-like metal plate 10 b respectively. This is the step that isgenerated by the stress (internal stress) caused in the metal plate initself. Normally the flatness is in proportion to square of the area.Thus, since the area of the above bonded portion 10 z of the metal plate10 is considerably larger than the area in the measured infinitesimalarea, it can be easily understood that the step is well over 50 μm in anabsolute value.

[0072] Then, in order to validate the effect of the planarizing processaccording to the metal plate shaping method of the present embodiment,in the situation that the ring-like metal plates 10 b are fitted intoand clamped by the clamping jig 40, the planarizing process was carriedout by executing the thermal treatment according to the similar methodto the above method.

[0073] According to this result, as shown in FIGS. 8A to 8C, the stepsin above three infinitesimal areas were suppressed smaller than about ±5μm respectively. Thus, it was confirmed that the metal plate shapingmethod of the present embodiment is effective to improve the flatness ofthe surface of the metal plate.

[0074] Also, when hardness of the surface of the ring-like metal plate10 b, to which the planarizing process has been applied, was measured bythe Vickers hardness tester, the Vickers hardness (Hv) of about 210obtained before the planarizing process is applied was reduced to about190 after the planarizing process. This means that the stress (internalstress) of the ring-like metal plate 10 b is removed and the surface isplanarized.

[0075] Next, the inventors of this application intentionally bent thering-like metal plate 10 b shown in FIG. 6 and then executed theplanarizing process according to the metal plate shaping method of thepresent embodiment. This is because the flatness of the surface of themetal plate is not only decided by the stress (internal stress) causedin the metal plate in itself but also deteriorated by the stress appliedby the stamping.

[0076] As shown in FIG. 9A, when the ring-like metal plate 10 b is bentby applying the stress, the step of about 120 μm was generated upwardlyin an absolute value. As the result that the planarizing process wasapplied to this metal plate by the similar method to the above method,as shown in FIG. 9A or 9C, conversely the step of about 15 μm wasgenerated downwardly, nevertheless it was confirmed that such processhas the effect on the improvement of the flatness. In this case, FIG. 9Cis prepared by mating a scale of an ordinate (flatness) of FIG. 9B withordinates (flatness) of FIG. 7 and FIG. 8.

[0077] (Second Embodiment)

[0078]FIG. 10 is a sectional view showing a metal plate shaping methodaccording to a second embodiment of the present invention. A differenceof the second embodiment from the first embodiment is that a pluralityof metal plates 10 are fitted into the clamping jig 40 in the state thata spacer is inserted between their bonded portions 10 z respectively.Since other steps are similar to those in the first embodiment, theirdetailed explanation will be omitted herein.

[0079] As described above, in the first embodiment, if a plurality ofmetal plates 10 are stacked, the pushed portions 10 x contact mutually.Thus, such a case is supposed that, if the number of stacked sheets ofthe metal plates 10 is increased, the lower metal plates 10 are deformedparticularly by their weights. The metal plate shaping method accordingto the second embodiment is provided to overcome such disadvantage.

[0080] In the metal plate shaping method according to the secondembodiment, first the same plate as the metal plate 10 shown in FIG. 1Bis formed by the similar method to the first embodiment. Then, as shownin FIG. 10, a plurality of metal plates 10 are stacked while inserting aspacer 70 between the bonded portions 10 z respectively. This spacer 70is made of cemented carbide hard metal, ceramic, or the like and has aring-like shape that corresponds to the bonded portion 10 z of the metalplate.

[0081] At this time, since the spacer 70 is arranged between the bondedportions 10 z of a plurality of metal plates 10, the pushed portion 10 xof the metal plate 10 is arranged high by a thickness of the spacer 70.As a result, not only a clearance 13 is present between their rolledportions 10 y of a plurality of metal plates 10, but also a clearance 13a is present between their pushed portions 10 x. Thus, unlike the firstembodiment, a plurality of metal plates except the bonded portions 10 zdo not come into contact mutually.

[0082] The metal plates 10 are stacked in this manner, and then thethermal treatment is applied in the state that the bonded portions 10 zof the metal plates 10 are being pushed by the predetermined forceaccording to the similar method to the first embodiment. Thus, the metalplate 10 serving as the back cap is manufactured.

[0083] According to the metal plate shaping method in the secondembodiment, even if a large number of metal plates 10 are stacked,portions of the metal plates 10 except the bonded portions 10 z are notbrought into contact mutually. Thus, there is no possibility that thedisadvantage of the deformation of the stacked metal plates is caused.Therefore, for example, 100 sheets or more of the metal plates 10 can bestacked and fitted into the clamping jig 40, and then the thermaltreatment can be applied collectively to these metal plates 10. As aresult, a production efficiency can be improved.

[0084] (Third Embodiment)

[0085]FIGS. 11A to 11E are sectional views showing a metal plate shapingmethod according to a third embodiment of the present invention. Adifference of the third embodiment from the second embodiment is that,when a plurality of metal plates 10 are stacked, portions of the metalplates 10 except the bonded portions 10 z are not brought into contactmutually without the spacer. Since other steps are similar to those inthe first embodiment, their detailed explanation will be omitted herein.

[0086] As described above, in the first embodiment, such a case issupposed that, if a plurality of metal plates 10 is stacked, the metalplates 10 are deformed by their weights. The metal plate shaping methodaccording to the third embodiment is provided to overcome suchdisadvantage without the insertion of the spacer.

[0087] In the metal plate shaping method according to the thirdembodiment, as shown in FIG. 11A, first the metal plate 10 a that has afilm thickness of about 0.25 to 0.3 mm is prepared, like the firstembodiment. Then, as shown in FIG. 11B, a pattern (not shown) of aresist film is formed on a predetermined peripheral portion serving asthe bonded portion of the metal plate 10 a. Then, the metal plate 10 ais etched to a depth of about 50 to 150 μm by the wet etching whileusing this resist film as a mask. Thereby, a thin body portion is formedin the metal plate 10 a In this case, the thin body portion of the metalplate 10 a may be formed by stamping instead of etching.

[0088] Then, as shown in FIG. 11C, a die 26 x having the punch 20, theclamping member 22, and the supporting member 24 is prepared. Then, themetal plate 10 a is inserted into the die 26 x to direct its etchedsurface to the punch 20 side, and then the metal plate 10 a is pushed bythe punch 20. Accordingly, as shown in FIG. 11D, the etched portion ofthe metal plate 10 a is pushed to form the pushed portion 10 x and therolled portion 10 y, and as a result the concave portion 11 is formed,thereby the metal plate 10 is obtained.

[0089] Then, as shown in FIG. 11E, plural sheets of metal plates 10 arestacked on the lower plate 12 of the clamping jig 40 by the similarmethod to the first embodiment. At this time, the pushed portion 10 xand the rolled portion 10 y are etched previously and their thicknessesare reduced rather than the bonded portion 10 z. Therefore, as alsoshown in FIG. 11E, the pushed portion 10 x and the rolled portion 10 yof plural metal plates 10 do not contact mutually and the clearances 13,13 a are provided between the metal plates 10 respectively.

[0090] A plurality of sheets of metal plates 10 are stacked in thismanner, and then the thermal treatment is applied in the state that thebonded portions 10 z of the metal plates 10 are being pushed by thepredetermined force according to the similar method to the firstembodiment. Thus, the metal plate 10 serving as the back cap ismanufactured.

[0091] According to the third embodiment, like the second embodiment,even if a large number of metal plates are stacked, portions of themetal plates except the bonded portions 10 z are not brought intocontact mutually. Thus, such a possibility can be eliminated that thedisadvantage of the deformation of the stacked metal plates is caused.Therefore, for example, 100 sheets or more of the metal plates 10 can bestacked and fitted into the clamping jig 40, and then the thermaltreatment can be applied collectively to these metal plates 10.

[0092] In addition, since there is no need to insert the spacers betweena plurality of metal plates 10, an operation of fitting a plurality ofmetal plates 10 into the clamping jig 40 can be simplified. As a result,a production efficiency can be further improved.

[0093] (Fourth Embodiment)

[0094]FIGS. 12A to 12D are sectional views showing a metal plate shapingmethod according to a fourth embodiment of the present invention. Adifference of the metal plate shaping method in the second embodimentfrom the first to third embodiments is that a concave portion is formedin the metal plate by the etching without use of the stamping.

[0095] In the first to third embodiments, the mode in which the thinmetal plate (e.g., 0.25 to 0.3 mm) is employed is exemplifiedrespectively. However, it is difficult to work a thick metal plate(e.g., 0.7 to 0.8 mm) by the stamping. Therefore, in the fourthembodiment, the concave portion is formed by applying the half-etchingto the metal plate in the thickness direction.

[0096] In the metal plate shaping method of the fourth embodiment, asshown in FIG. 12A, first a metal plate 10 a having a thickness of about0.7 to 0.8 mm, for example, is prepared. Then, as shown in FIG. 12B, aresist film 15 is patterned on the predetermined peripheral portionserving as the bonded portion 10 z of the metal plate 10 a, and then themetal plate 10 a is etched by the wet etching while using this resistfilm 15 as a mask. Thus, as shown in FIG. 12C, the concave portion 11having a depth of about 0.5 mm is formed and also the bonded portion 10z is defined, thereby the metal plate 10 is obtained.

[0097] Then, as shown in FIG. 12D, the metal plates 10 are fitted intothe clamping jig 40 such that the bonding surface 10 s of the metalplate 10 is directed to the lower plate 12 side. Then, the thermaltreatment is executed in the state that the bonded portions 10 z of aplurality of metal plates 10 are being pushed by the predeterminedforce. Thus, the metal plate 10 serving as the back cap is manufactured.

[0098] According to the fourth embodiment, the metal plate having alarge thickness can be easily applied as the back cap of the organic ELdisplay device. Also, like the second and third embodiments, even if alarge number of metal plates are stacked, portions of the metal platesexcept the bonded portions 10 z are not brought into contact mutually.Thus, there is no possibility that the disadvantage of the deformationof the metal plates is caused. Therefore, for example, 100 sheets ormore of the metal plates 10 can be stacked and fitted into the clampingjig 40, and then the thermal treatment can be applied collectively tothese metal plates 10. In addition, unlike the second embodiment, thereis no need to insert the spacer between the bonded portions 10 z of aplurality of metal plates 10.

What is claimed is:
 1. A metal plate shaping method comprising the stepsof: preparing a plurality of metal plates that have a concave shape in acenter principal portion except a predetermined peripheral portion; andexecuting a thermal treatment to the plurality of metal plates in such astate that the plurality of metal plates are stacked to mate thepredetermined peripheral portion with each other and also predeterminedperipheral portions are pushed.
 2. A metal plate shaping methodcomprising the steps of: preparing a metal plate that has a concaveshape in a center principal portion except a predetermined peripheralportion; and executing a thermal treatment to the metal plate in such astate that the predetermined peripheral portion is pushed.
 3. The metalplate shaping method according to claim 1, wherein the step of preparingthe plurality of metal plates includes the step of forming the concaveshape by pushing the center principal portion of a metal plate by virtueof a stamping.
 4. The metal plate shaping method according to claim 1,wherein the step of preparing the plurality of metal plates includes thesteps of, reducing a thickness by etching the center principal portionof a metal plate, and forming the concave shape by pushing the centerprincipal portion of the metal plate by virtue of a stamping.
 5. Themetal plate shaping method according to claim 1, wherein the step ofpreparing the plurality of metal plates includes the step of forming theconcave shape by etching the center principal portion of a metal plateto reduce a thickness.
 6. The metal plate shaping method according toclaim 1, wherein, in the step of executing the thermal treatment, theplurality of metal plates are stacked to insert a spacer between thepredetermined peripheral portions.
 7. The metal plate shaping methodaccording to claim 1, wherein the metal plate is formed of any oneselected from a group consisting of an alloy of nickel (Ni) and iron(Fe), an alloy of nickel (Ni), iron (Fe) and cobalt (Co), tungsten (W),and molybdenum (Mo).
 8. The metal plate shaping method according toclaim 1, wherein the thermal treatment is executed at a temperature of600 to 800° C.
 9. The metal plate shaping method according to claim 1,wherein the thermal treatment is executed in an atmosphere of anonoxidizing gas.